New generation consumer devices increasingly rely on touch screen inputs such as virtual buttons and sliders displayed on a screen as an alternative to physical inputs. Users may interface with such devices almost exclusively by touching and/or otherwise manipulating the virtual buttons, sliders, scrollers, and the like on the screen with one or more finger(s). Graphic displays on the screen provide visual feedback responsive to such manipulation. In some more recent touch screen devices, force feedback or tactile feedback, commonly collectively known as haptic feedback, can also be provided to a user as the user's fingers interact with virtual objects on the touch screen. This is accomplished generally by moving or vibrating the screen with a haptic actuator coupled to the screen.
To allow the haptic touch screen to move in response to the haptic actuator and thereby to isolate a haptic effect to the screen, haptic touch screens have been compliantly suspended within electronic devices in which they reside. It is important, however, that, even though the screen must be able to move when the haptic actuator is activated, the suspended screen must nevertheless feel to a user as if it were substantially rigidly mounted when touched. Others have addressed the problem by not using a suspension, but not using a suspension limits the mass of the system that can have haptic effects.
Suspensions utilizing compliant grommet for mounting touch screens and touch surfaces within a housing are known, as illustrated in U.S. patent application Ser. No. 13/049,265 to Olien et al., filed Mar. 16, 2011, herein incorporated by reference in its entirety. More particularly, FIG. 1 reproduced from Olien et al. illustrates an exploded view of various components of an electronic touch screen system 100 for providing haptic feedback to a touch screen 102 that utilizes a plurality of grommet suspension elements 104 in a compliant suspension system. In addition to touch screen 102, touch screen system 100 includes a carrier 106, a motor or haptic actuator 108, a dust seal 110, an LCD component 112, and a main housing component 114. Grommet suspension elements 104 are configured to allow preferential movement of touch screen 102 in a certain direction, such as an −x direction, while limiting movement in other directions, such as the y- and z-directions.
Haptic actuator 108 may be any of a number of known actuator types including, without limitation, a piezo actuator, voice coil actuator, an eccentric mass actuator, an E-core type actuator, a solenoid, a moving magnet actuator, or other type of actuator as desired. Piezoelectric actuators have the property of developing an electric charge when mechanical stress is exerted on them. A piezoelectric actuator 208 is shown in FIG. 2 as available from a commercial manufacturer. Piezoelectric actuator 208 includes a flat intermediate substrate 209 and two segments 207 of piezo material bonded or otherwise coupled to both sides of substrate 209, as best shown in the exploded view of FIG. 2A. When mechanical stress is exerted onto segments 207 of piezo material, piezoelectric actuator 208 develops an electric charge and bends as shown in FIG. 2B. The operation of piezoelectric actuators to output force based on an input electrical signal is well known to those skilled the art. In order to attach piezoelectric actuator 208 to a haptic system, the entire actuator unit or assembly including substrate 209 and segments 207 of piezo material is clamped onto the system. A clamp (not shown) for coupling the actuator to the system may be designed or integrated into a system component or may be a separate clamp component.
In addition to compliant grommet components, other suspensions have been proposed for touch screen applications as illustrated in U.S. Pat. Appl. Pub. No. 2008/0111788 A1 to Rosenberg et al., herein incorporated by reference in its entirety, and U.S. Pat. Appl. Pub. No. 2010/0245254 A1 to Olien et al, herein incorporated by reference in its entirety. FIG. 3, which is reproduced from Rosenberg et al., illustrates a touch screen system 300 having one or more spring elements 304 coupled between a touchpad or touch screen 302 and a main housing component 314. Spring elements 304 are shown as helical or coiled elements, but may be a compliant material such as rubber, foam, or flexures. Spring elements 304 couple touch screen 302 to the rigid housing 314 of system 300 and allow touch screen 302 to be moved along the z-axis. In the embodiment of FIG. 3, one or more piezoelectric actuators 308 are coupled to the underside of a touch screen 302 and serve to output a small pulse, vibration, or texture sensation onto touch screen 302 and to the user if the user is contacting the touch screen.
A need exists in the art for improved and/or alternative compliant suspension systems for haptic touch screens.